20 Most Recent Hitachi EC12 Portable Electric 2hp Air Compressor, Oil Lubricated Questions & Answers


The head pressure is released thru the needle unloader valve at the pressure switch. Notice a 1/4 inch plastic tube (or metal) running from the intank check valve to the pressure switch. After pressure switch reaches set pressure a small tang moves up and presses on the needle valve releasing the pressure. Only a small amount of air will be released. If however air continues to escape from the needle valve, then the check valve is bad.

Hitachi EC12... | Answered on Jan 21, 2019


This problem is caused by either the starter capacitor or the in-tank check valve. Ez to check. With no air in tank, start compressor; if motor hums or has difficulty suspect capacitor. If motor starts, partially fill tank and unplug the power. Check for air leaking at the pressure switch or air coming out of the air inlet (remove the air filter). If air leaking, replace check valve. If no air leaking, again let out all the from the tank and connect power. Allow the compressor to fill and shut-off. After the compressor fills, again listen for air leaking from the pressure switch unloader valve. If air continues to leak from unloader, replace the check valve. Good luck

Hitachi EC12... | Answered on Nov 22, 2016


The EC12 actually draws approximately 15.5 amps when starting, so you are best served to use without extention cord on a 20 amp circuit. One thing that will improve operation, is to use 5w-50 full sinthetic oil. Fill to notch in dipstick. If possible change your overload switch to a 20 amp. It is currently a 15 amp. (cause right there for continual overload). I unplugged my reset button and added a piece of #12 coated wire as a jumper (do this at your own risk), but I've been fine for three years now. #12 wire fits right into the clips that attach to the reset button. Good luck.

Hitachi EC12... | Answered on Dec 27, 2015


It sounds like the air pressure assembly unit is not reading the pressure drop. some of these units have adjustments under the covers and be reset.

Hitachi EC12... | Answered on Jul 09, 2015


Put in the best grade oil for small high RPM engines

Hitachi EC12... | Answered on Jun 12, 2015


Cheap oil-less compressor, normal.
If you don't like it, buy one that uses oil and a drive belt.

Hitachi EC12... | Answered on Feb 26, 2015


Hitachi builds a very nice compressor, however suffers from the same problem that all brands will eventually encounter. Failure of the pressure switch. The pressure switch is a very hard working component of the unit. Depending on use, the pressure switch may cycle from as little as two or three cycles a day to as many as dozens per hour. The pressure switch has springs, contacts and unloader features that eventually wear out. The two most common failures are the contacts and the rubber diaphragm that acts against the springs to shut the unit down. Sometimes the screws securing the base of the switch the inlet port come loose and cause the problem that you are having. (The rubber diaphragm is between the base inlet port and the switch) Simple test is to spray soapy water around base of switch to check for leaks. Replace the switch as necessary with a SquareD brand available at www.grainger.com instead of factory unit to save money and increase life. You may have to make simple modifications however the money saved will be worth it. Choose a pressure switch with cut-off range between 120-139 psi. The higher the cutout switch setting you choose the shorter lifespan for your compressor. Your compressor works harder and gets hotter when achieving higher pressures. Try to use either no extension or shortest cord possible to max life of unit and compressor oil instead of motor oil to prevent carbon deposits. Good luck and email if you have questions about your Hitachi.

Hitachi EC12... | Answered on Jan 09, 2015


The problem that you describe is most likely the in-tank check valve (brass or chrome valve where air enters tank ). Easy to check. Run compressor till you have about 60-80 lbs in tank then shut-off / unplug for safety. Remove the small hose (1/4) at the check valve and verify that air is leaking from valve. If leaking remove cap from checkvalve and look at inner plastic valve for cracks. Replace as needed then re-test for leaks. You can be creative in making the inner plastic valve (teflon or nylon ball 1/2 - 5/8 ) or replace the whole valve. (inner part not sold separately) Good luck with your repair and post again if you have a question.

Hitachi EC12... | Answered on Apr 24, 2014

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